Electrically conductive organic polymers have been of scientific and technological interest since the late 1970's. These relatively new materials exhibit the electronic and magnetic properties characteristic of metals while retaining the physical and mechanical properties associated with conventional organic polymers. Herein we describe electrically conducting polyparaphenylenes vinylenes, polyparaphenylenes, polyanilines, polythiophenes, polyazines, polyfuranes, polypyrroles polyselenophenes, poly-p-phenylene sulfides, polyacetylenes formed from soluble precursors, combinations thereof and blends thereof with other polymers and copolymers of the monomers thereof. In order for these materials to be used in place of metals in more applications, it is desirable to increase the conductivity of these materials.
The article “The Concept of Secondary Doping as Applied to Polyaniline”, A. G. MacDiarmid, A. J. Epstein, Synthetic Metals, 65 (1994), 103-116, describes increasing the electrical conductivity of a polyaniline by exposing a doped polyaniline to a secondary dopant, such as meta-cresol. MacDiarmid et al. teaches that the secondary dopant results in an intra-molecular conformational change in the polyaniline molecule. Prior to being exposed to the secondary dopant, the doped polyaniline molecule is in a compact coil intra-molecular conformation. Intra-molecular conformation refers to the conformation of a single molecule or a single polymer chain in which the molecular chain is coiled around itself. In contra-distinction inter-molecular structure refers to the structural arrangement of more than one molecule or polymer chain in which the molecules or chains are bonded together or coiled around each other forming aggregates. These aggregates are then comprised of many polymer chains intertwined or entangled. MacDiarmid et al. teaches that the secondary dopant causes a intra-molecular conformational change, i.e., the molecule or the chain unravels and assumes an expanded coil conformation. A film of this expanded coil polyaniline has enhanced electrical conductivity because of an increase in the crystallinity of the material formed from the aggregated straightened molecules.
In the article “Transport studies of protonated emeraldine powder: A granular polymeric metal system”, F. Zuo et al., Phys. Rev. B 36, 3475 (1987) it has been reported that the polyaniline which has been doped has electrically conductive regions or islands which are of the order of 200-300 Å. The spaces between these regions are significantly less electrically conductive. When an electrical current flows along the polyaniline molecules, current flows through the electrically conductive regions and hops over the less electrically conductive region to an adjacent electrically conductive region.
It is an object of the present invention to increase the electrical conductivity of electrically conductive polymers.
It is another object of the present invention to enhance the electrical conductivity of an electrically conductive polymer by deaggregating aggregated molecules which are precursors of the electrically conducting polymers so that the molecules can be more uniformly doped.
It is another object of the present invention to deaggregate polymer molecules prior to being doped to the electrically conducting state.
It is another object of the present invention to lower the glass transition temperature of the precursor to an electrically conductive polymer and of an electrically conductive polymer by the addition of deaggregating agents.
It is another object of the present invention to increase the electrical conductivity of electrically conductive polymers by extending the electrically conductive regions or islands of the electrically conductive polymer.
It is another object of the present invention to further increase the electrical conductivity of a deaggregated electrically conductive polymer by stretch orientation.
It is another object of the present invention to increase the shelf-life of a precursor to an electrically conductive polymer and of an electrically conductive polymer by the addition of deaggregating agents.